SYLVANIA, Ohio --Now that she's officially a millionaire, Lydia Ko joked she'll have to keep a closer watch on where her paychecks go.

"I'll probably see that going into my mom's account," she said with a laugh, referring to the US$210,000 she got for winning Sunday's Marathon Classic.

The 17-year-old broke free from a late tie with So Yeon Ryu, hitting a wedge to 4 feet for birdie on the 72nd hole to take the lead. Then she tried in vain — she's just 5-foot-5 — to see past the large gallery at 18 as Ryu missed a 6-foot birdie putt on the final hole that would have forced a playoff.

"I couldn't see it properly. I was behind some people," she said after her second LPGA Tour victory that matched the two Canadian Open titles she won as an amateur. "But I kind of could tell what happened by the crowd's reaction."

She became the youngest player to top US$1 million in career earnings on the LPGA Tour. Ko is roughly 17 months younger than Lexi Thompson, previously the youngest. Ko has shown incredible consistency in her rookie year on tour, making the cut in all 15 tournaments she's entered. She has six top-10 finishes in addition to her wins, with five of those being top-fives.

Ryu had poured in a big-breaking, 25-foot birdie putt on the 17th to pull even.

But then Ko stuck her approach at the par-5 closing hole and calmly rolled in the birdie putt for a 6-under 65 that left her at 15-under 269.

Ryu hit a brilliant third shot to the green, but pushed her 6-footer at the 18th.

"Absolutely I'm disappointed I missed (that) birdie putt," she said. "Sometimes if I get something lucky, then I get something that is unlucky. I just accept it and let it go."

Ko was resilient, also shrugging aside a challenge from veteran Cristie Kerr, who pulled into a tie with her on the homeward nine.